Does Time Machine Copy UNCHANGED files over and over??

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Does Time Machine Copy UNCHANGED files over and over??

Okay, it seems to me that whatever files I have selected for backup are copied by Time Machine EVERY SINGLE TIME it backs up my Mac, instead of just when I make changes to them. Is that correct? If so, that just seems to be a massive waste of space on the external hard drive, and is probably the reason my 1TB drive runs out of space so quickly.

For example, I don't need 50 copies of my iTunes Library. I just need ONE copy. Time Machine should back up the music files ONCE, and if I add more songs to iTunes, it should then detect it and backup JUST the new files. Same thing with a Word document or whatever...make ONE copy of the file and then if I ALTER the file, make a copy of the ALTERED FILE.

Am I making sense here or is this just wishful thinking? Is there a way to make these types of adjustments in settings that I am missing?

Thanks!

Mac OS X (10.5.8)

Posted on Aug 26, 2009 10:23 PM

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Answer 1

Aug 26, 2009 10:39 PM in response to Shugama

Hello S:

TM only copies files/data that changed since the last backup. Incremental backups are normally quite small and consume very little space.

I suggest you download a widget (Time Machine Buddy) and take a look at what is happening. The widget gives near real time access to the TM log file.

Barry

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Answer 2

dbsneddon

Level 4

1,542 points

Aug 26, 2009 10:41 PM in response to Shugama

You say you have a 1TB external drive but mention nothing about the internal
drive - how big? - how much used?

Time Machine only makes one copy of the file and if it doesn't change the next
backup creates a link to the file, not another copy. If a file changes then a new
copy will be created and the original one will be preserved. When the Time Machine
disk fills up it will start deleting the oldest backups.

Have you checked the Apple site for details on how Time Machine works or
checked elsewhere for the details?

Dave

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Answer 3

Shugama Author

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Aug 27, 2009 6:00 AM in response to dbsneddon

I have a 500GB drive on my iMac, and it appears the size of the selected backup files is approx 150GB.

I have checked out the documentation and it doesn't jive with what I see happening if I use Finder to physically check out what's on the external drive. On the oldest available backup (which ONLY dates back to August 16 '09), I find a raw music file that's 850MB, last modified in November of 2007. I haven't touched the file since then, but I see the file physically taking up 850MB of space on my external HD for EVERY backup that's listed in Finder (they are NOT "links" to the file).

null

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Answer 4

dbsneddon

Level 4

1,542 points

Aug 27, 2009 6:09 AM in response to Shugama

The files "appear" to take up the space because they are hard links.

What are you expecting to see?

Each backup will appear to be "real".

Do some more research.

Dave

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Answer 5

V.K.

Level 9

56,192 points

Aug 27, 2009 6:12 AM in response to Shugama

Shugama wrote:
Okay, it seems to me that whatever files I have selected for backup are copied by Time Machine EVERY SINGLE TIME it backs up my Mac, instead of just when I make changes to them. Is that correct?

no, that's wrong. that would indeed be a huge waste of space. TM only backs up afresh new and changed files since the last backup. everything else is *hard linked* to existing backup copies. read up on what a hard link is.
http://en.wikipedia.org/wiki/Hard_link

that's why incremental backups take very little space and yet every single TM backup is a full and completely independent copy of your system at the backup time. and that's why you can have a lot of TM backups fit on your backup drive.

If so, that just seems to be a massive waste of space on the external hard drive, and is probably the reason my 1TB drive runs out of space so quickly.

For example, I don't need 50 copies of my iTunes Library. I just need ONE copy. Time Machine should back up the music files ONCE, and if I add more songs to iTunes, it should then detect it and backup JUST the new files. Same thing with a Word document or whatever...make ONE copy of the file and then if I ALTER the file, make a copy of the ALTERED FILE.

Am I making sense here or is this just wishful thinking? Is there a way to make these types of adjustments in settings that I am missing?

Thanks!

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Answer 6

Shugama Author

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Aug 27, 2009 7:11 AM in response to dbsneddon

Hmmm...I guess that is why there are only TEN backups on my 1TB external drive before it is FULL.

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Answer 7

dbsneddon

Level 4

1,542 points

Aug 27, 2009 7:34 AM in response to Shugama

If that is indeed the case then there is more to the picture
than you are telling us...

Dave

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Answer 8

V.K.

Level 9

56,192 points

Aug 27, 2009 7:42 AM in response to Shugama

the exact amount included in backups is listed in TM system preferences->options. even if it's just 150GB as you say how do you suppose 10 backups fit on a 1 TB drive? we told you how TM works and normally incremental backups take very little space. if yours are abnormally large there you should check what exactly is being backed every time get TimeTracker
TimeMachineTracker
and see what it says. also TimeMachine buddy widget will tell you how big every incremental backup actually is.

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Answer 9

Shugama Author

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Aug 27, 2009 8:59 AM in response to V.K.

I installed the TimeMachine Buddy as suggested. It appears that it is making a NEW backup of a 65GB disk image I created for my iPhoto library every day instead of just backing up the files on the disk image. I guess there's no way to get TM to backup only the actual files on the disk image instead of the entire disk image itself, is there? There don't seem to be a lot of options to tweak in the TM settings.

If you're going to ask why I have the disk image set up, it is so multiple user accounts on the iMac can have access to the same iPhoto library, regardless of what user login is being used. That was the only way I could set it up to work (permissions for all users to access the main account's iPhoto library would not work).

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Answer 10

V.K.

Level 9

56,192 points

Aug 27, 2009 9:04 AM in response to Shugama

a regular disk image will be treated by TM as a single file and if you make ANY changes to it Tm will back it up from scratch. you can use a sparse bundle disk image instead. sparse bundles were introduced in Leopard to deal with this exact issue. a sparse bundle is split in a large number of small bands and TM will only back up changed bands. for a different method of sharing iphoto library between different users see this link.
http://discussions.apple.com/thread.jspa?messageID=9941550#9941550

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Answer 11

Shugama Author

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Aug 27, 2009 9:22 AM in response to V.K.

Thanks. I'll be checking into this to see if I can get it to work. Thanks for all the help. 🙂

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Answer 12

Shugama Author

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Aug 27, 2009 11:33 AM in response to V.K.

This worked (below). I tried endlessly to get this to work in iPhoto '08, but it looks like they solved the issue in '09 (unbeknownst to me until now). Now I can get rid of the disk image which solves my Time Machine issue.

Thanks for all the help.

Sharing via the Shared Folder -- Another major annoyance with versions of iPhoto prior to iPhoto '09 was that you couldn't just put your iPhoto Library in the /Users/Shared folder to share it among multiple accounts on the same Mac, since iPhoto always set the permissions on thumbnails to the account that imported the photos, preventing other accounts from editing those photos and having the edits reflected in the thumbnails.

That limitation has now been fixed in iPhoto '09, so you can share an iPhoto library merely by moving it to /Users/Shared and then double-clicking it to open in iPhoto from each account. You may be prompted to repair permissions on the first access - click the Repair button to do that. Note that this also works for storing an iPhoto library on an external hard disk that's shared among users or on a network volume for access across a fast network.

Only one person may access a shared iPhoto library at a time.

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